A rotating shaft, an air circulating machine, and a manufacturing method of a rotating shaft

Abstract

This invention provides a rotating shaft, an air circulator, and a method for manufacturing the rotating shaft. The rotating shaft includes a base shaft with a hard film covering its surface. The hard film has a higher hardness than the base shaft. A copper film with a lower hardness than the base shaft is disposed between the base shaft and the hard film. This invention solves the technical problem of high residual stress in the H-DLC film on the surface of the rotating shaft in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of rotating shaft technology, specifically relating to a rotating shaft, an air circulator, and a method for manufacturing the rotating shaft. Background Technology

[0002] The turbine drive shaft of the air circulator is supported by a pneumatic bearing. Therefore, during start-up and shutdown, dry friction occurs between the drive shaft and the bearing foil. This dry friction easily removes material from the shaft surface, leading to significant vibration during shaft rotation. To address this issue, a hydride diamond-like carbon (H-DLC) film is used to modify the surface of the drive shaft, with alloy steel as the base material. The H-DLC film is manufactured at high temperatures (approximately 500°C). When cooled to room temperature (approximately 25°C), due to the significant difference in thermal expansion coefficient between the H-DLC film and its substrate, substantial residual stress is generated. This stress makes the H-DLC film prone to brittle fracture under impact.

[0003] How to reduce the residual stress of the H-DLC film on the surface of the rotating shaft is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] Therefore, the present invention provides a rotating shaft, an air circulator, and a method for manufacturing the rotating shaft, which can solve the technical problem of large residual stress on the H-DLC film on the surface of the rotating shaft in the prior art.

[0005] In a first aspect, the present invention provides a rotating shaft, including a base shaft, the surface of which is covered with a hard film, the hardness of which is greater than the hardness of the base shaft, and a copper film is disposed between the base shaft and the hard film, the hardness of which is less than the hardness of the base shaft.

[0006] In some embodiments, the hard film is diamond-like hydrogen.

[0007] In some embodiments, the thickness of the copper film is H1, then 0.003mm≤H1≤0.004mm.

[0008] In some embodiments, the thickness of the hard film is H2, then 0.003mm≤H2≤0.004mm.

[0009] Secondly, the present invention provides an air circulator, including an air dynamic bearing and the aforementioned rotating shaft, wherein the top foil of the air dynamic bearing is opposite to the outer peripheral surface of the rotating shaft.

[0010] Thirdly, the present invention also provides a method for manufacturing a rotating shaft, the method being used for manufacturing the rotating shaft;

[0011] The manufacturing method includes: Step 1, treating the surface of the base shaft; Step 2, manufacturing a copper film on the surface of the base shaft; Step 3, manufacturing a hard film on the surface of the copper film.

[0012] In some embodiments, the base shaft is an iron base shaft, and step one includes, S11: grinding the surface roughness of the base shaft to no greater than Ra0.08;

[0013] S12: Clean the surface of the base shaft for 9-11 minutes, then clean it with ultrasound for 14-16 minutes, and finally blow it dry.

[0014] In some embodiments, step two includes,

[0015] S21: Place the copper target on top of the magnetron sputtering chamber and evacuate the chamber to a pressure not exceeding 5 × 10⁻⁶. - 5 Pa;

[0016] S22: Apply a voltage of -348V to -352V to the copper target, while sputtering the copper target with argon gas at a flow rate of not less than 30 sccm, and maintain the pressure in the magnetron sputtering chamber at 0.4Pa to 0.5Pa. This process lasts for 2.5 to 3.5 minutes.

[0017] S23: Stop applying voltage to the copper target, place base shaft 1 on top of the magnetron sputtering chamber, and evacuate the magnetron sputtering chamber to a pressure not exceeding 5 × 10⁻⁶. -5 At the same time, argon gas continues to sputter the copper target at a flow rate of not less than 30 sccm, while maintaining the pressure in the magnetron sputtering chamber at no more than 0.5 Pa and the temperature in the sputtering chamber between 50°C and 80°C. This process lasts for 45 to 55 minutes.

[0018] In some embodiments, S12 includes: cleaning the surface of the base shaft with acetone, ultrasonically cleaning with anhydrous ethanol, and drying with nitrogen.

[0019] In some embodiments, the rigid film is an H-DLC film, and step three includes:

[0020] S31: Replace the copper target with a graphite target with a purity of not less than 99.9% and place it on top of the magnetron sputtering chamber. Evacuate the magnetron sputtering chamber to a pressure not exceeding 5 × 10⁻⁶. -5 Pa, with a temperature range of 480℃ to 520℃;

[0021] S32: Apply a base bias voltage of -348V to -352V to the graphite target, while sputtering a mixture of argon and methane at a flow rate of not less than 150 sccm, wherein the ratio of argon to methane is between 2.2 and 2.5, and the process lasts for 20 to 25 hours.

[0022] In some embodiments, step three further includes,

[0023] S33: Cool the temperature inside the sputtering chamber to between 25°C and 30°C at a rate of (0.3 to 0.4)°C / min.

[0024] A copper film is placed between the base shaft and the hard film. Since the hardness of copper is lower than that of the base shaft and the hard film, the copper film can alleviate the high residual internal stress generated in the hard film when cooling from the high-temperature preparation environment to room temperature due to the mismatch in thermal expansion coefficients. The shaft using a copper film as an intermediate transition layer has good film-substrate adhesion and wear resistance. Attached Figure Description

[0025] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0026] Figure 1 This is a schematic diagram showing the relationship between the rotating shaft and the air dynamic bearing in an embodiment of the present invention;

[0027] Figure 2 This is an axial schematic diagram of the rotating shaft according to an embodiment of the present invention;

[0028] Figure 3 This is a radial cross-sectional schematic diagram of the rotating shaft according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the axial stress distribution of the H-DLC when cooled to 20°C, provided with a copper film and H-DLC in an embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram of the axial stress distribution at the interface between the H-DLC and the copper film in an embodiment of the present invention, when cooled to 20°C.

[0031] Figure 6 This is a schematic diagram of the axial residual stress at the interface between the H-DLC and the copper film when the H-DLC and the copper film are cooled to 20°C, provided in an embodiment of the present invention.

[0032] Figure 7 This is a schematic diagram of the axial stress distribution of H-DLC when cooled to 20°C, when the existing technology only has H-DLC.

[0033] Figure 8This is a schematic diagram of the axial stress distribution at the interface between the H-DLC and the base shaft when the base shaft is cooled to 20°C, which is the only existing technology that uses H-DLC.

[0034] Figure 9 This is a schematic diagram of the axial residual stress at the interface between the H-DLC and the base shaft when the base shaft is cooled to 20°C, which is the only existing technology that uses H-DLC.

[0035] The attached figures are labeled as follows:

[0036] 1. Base shaft; 2. Hard film; 3. Copper film; 4. Pneumatic bearing. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0039] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0040] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0041] The residual stress on the H-DLC film on the shaft surface is generated after the H-DLC film is prepared at the ambient temperature during magnetron sputtering and then cooled to room temperature. Specifically, during the preparation of the H-DLC film, the base shaft is subjected to a high temperature of approximately 500°C, at which the H-DLC film forms. At the same time, the base shaft (0Cr17Ni4Cu4Nb) is also in a state of volume expansion. At this time, the residual stress of the H-DLC film is relatively small, close to a stress-free state. After the preparation is completed, the shaft (including the H-DLC film) is cooled to room temperature. Due to the mismatch in the coefficients of thermal expansion between the shaft substrate and the H-DLC, the H-DLC film generates high residual stress. Excessive stress value will lead to a decrease in the bonding force between the H-DLC film and the base shaft, and the H-DLC is prone to brittle fracture when subjected to impact.

[0042] To reduce the residual stress of the H-DLC film on the surface of a rotating shaft, the present invention provides a rotating shaft and a method for manufacturing the rotating shaft.

[0043] like Figure 1-3 As shown, a rotating shaft includes a base shaft 1, the surface of which is covered with a hard film 2, the hardness of which is greater than that of the base shaft 1, and a copper film 3 is disposed between the base shaft 1 and the hard film 2, the hardness of which is less than that of the base shaft 1.

[0044] A copper film 3 is placed between the base shaft 1 and the hard film 2. Since the hardness of copper is lower than that of both the base shaft 1 and the hard film 2, the copper film 3 can alleviate the high residual internal stress generated in the hard film 2 when cooled from the high-temperature preparation environment to room temperature due to the mismatch in thermal expansion coefficients. The shaft using the copper film 3 as an intermediate transition layer exhibits good film-substrate adhesion and wear resistance. (See attached image) Figure 1-3 The rotating shaft structure with copper film 3 and hard film 2 is shown.

[0045] Copper can reduce interfacial residual stress for two main reasons: (i) the interface relaxation between copper and DLC allows the original interfacial residual stress to undergo plastic deformation and be converted into heat, thus reducing residual stress; (ii) copper does not form carbides with DLC, and copper atoms are only connected to carbon atoms through weak van der Waals forces.

[0046] Low residual stress requires materials with similar coefficients of thermal expansion and similar lattice constants. The lattice constant of copper is 0.36151 nm, and that of diamond is 0.357 nm. Since their lattice constants are similar, the high residual stress caused by the size mismatch of atomic interfaces due to the large difference in lattice constants during preparation and deposition will not occur.

[0047] Preferably, the rigid film 2 is an H-DLC film.

[0048] H-DLC is an abbreviation for H-Diamond-like carbon, which refers to hydrogenated diamond-like carbon.

[0049] Hydrogenated diamond-like carbon (H-DLC) has high hardness and good wear resistance. As a hard film 2 for the base shaft 1, it can improve the wear resistance of the base shaft 1, enabling the base shaft 1 to rotate stably.

[0050] Furthermore, the copper film 3 will not cause the SP3 hybrid bonds of the hard film 2 to transform into SP2 hybrid bonds, while the SP2 hybrid bonds will reduce the bonding force between the hard film 2 and the base shaft 1.

[0051] It can also prevent the iron element in the shaft of the iron-based alloy from catalyzing the Sp3 hybrid bonds of the hard film 2 to become Sp2 hybrid graphite, which would otherwise lead to a decrease in the film-substrate bonding strength.

[0052] Preferred, such as Figure 3 As shown, the thickness of the copper film 3 is H1, then 0.003mm≤H1≤0.004mm.

[0053] If the copper film 3 is too thin, for example, less than 0.003 mm, it is insufficient to reduce the residual stress of the H-DLC. If the copper film 3 is too thick, for example, greater than 0.004 mm, its own hardness is too low, and it cannot provide sufficient support for the H-DLC. When the H-DLC is subjected to impact, it is prone to deformation and fracture. Experiments have shown that a copper film 3 thickness between 0.003 mm and 0.004 mm yields the best results.

[0054] Preferred, such as Figure 3 As shown, the thickness of the hard film 2 is H2, then 0.003mm≤H2≤0.004mm.

[0055] If the thickness of the hard film 2 is too small, for example, less than 0.003 mm, it will be difficult to manufacture and its wear resistance will be insufficient, making it difficult to meet the application requirements. If the thickness of the hard film 2 is too large, for example, greater than 0.004 mm, the residual stress will be too high. A thinner copper film 3 cannot reduce the residual stress, while a thicker copper film 3 cannot provide sufficient support for the hard film 2. After testing, the thickness of the hard film 2 between 0.003 mm and 0.004 mm is the best.

[0056] The residual stress of H-DLC films without copper film layer 3 and with copper film layer 3 (intermediate transition layer) was compared by simulation. The actual temperature and mechanical environment of H-DLC films and H-DLC+copper films prepared by magnetron sputtering were simulated by finite element simulation, and the stress distribution of single-layer H-DLC films and single-layer H-DLC films + copper film layer 3 at room temperature was calculated.

[0057] Specifically, Figure 7 The axial stress distribution cloud map of the outer surface of the H-DLC film after preparation at 500℃ and cooling to room temperature (about 20℃) when there is no copper film 3. Figure 4 This is a contour map of the axial stress distribution on the outer surface of the H-DLC film after it has been prepared at 500°C and cooled to room temperature (approximately 20°C) with copper film 3 present; from Figure 4 and Figure 7 It can be seen that the surface stress of H-DLC is basically the same. Figure 8 This is a schematic diagram of the stress at the interface between the H-DLC and the base shaft when there is no copper film. Figure 5 This is a schematic diagram showing the stress at the interface between the H-DLC and the copper film 3 when copper film 3 is present; from Figure 8 It is evident that without the copper film, the axial stress of the H-DLC film is negative except at the edges, indicating that the H-DLC film is under compressive stress, while the substrate surface near the bonding surface is under tensile stress. Figure 5 and Figure 8 In comparison, it can be seen that the stress at the contact surface between H-DLC and copper film 2 is less than the stress at the contact surface between H-DLC and base shaft.

[0058] Without copper film 3, such as Figure 9 As shown, the maximum residual compressive stress (negative value) at the bonding surface of the H-DLC film is -2973.4 MPa; with copper film 3, as... Figure 6 As shown, the maximum residual compressive stress (negative value) at the bonding surface of the H-DLC film is -2645.5 MPa. Therefore, the H-DLC film with copper film 3 (intermediate transition layer) can effectively reduce the residual stress by about 11%. The lower residual stress can effectively enhance the film-substrate adhesion and avoid brittle fracture. The reason why the residual stress of H-DLC is smaller when copper film 3 is provided is as follows: First, copper has a lower Young's modulus and is more prone to greater strain; second, there are a large number of interfaces parallel to the substrate surface in the multilayer film. In the film system with alternating soft and hard layers, the intermediate soft layer (copper film 3 in this application) acts as a shear band, thus effectively reducing the internal stress and interface stress of the film layer; third, in the preparation of H-DLC film, diamond grains are anchored on the deep copper substrate, which also increases the film-substrate adhesion to a certain extent.

[0059] The base shaft 1 is preferably an iron base shaft 1, which can be a hollow shaft. The outer diameter φ1 of the base shaft 1 is between 132mm and 38mm, and the inner diameter φ2 of the base shaft 1 is between 26mm and 32mm.

[0060] The present invention provides an air circulator, including an air dynamic bearing 4 and a rotating shaft, wherein the top foil of the air dynamic bearing 4 is opposite to the outer peripheral surface of the rotating shaft.

[0061] The present invention provides a method for manufacturing a rotating shaft, the method being used for manufacturing the aforementioned rotating shaft;

[0062] The manufacturing method includes: Step 1, treating the surface of the base shaft; Step 2, manufacturing a copper film on the surface of the base shaft; Step 3, manufacturing a hard film on the surface of the copper film.

[0063] Preferably, the base shaft 1 is an iron-based shaft 1, and step one includes:

[0064] S11: Grind the surface roughness of base shaft 1 to no greater than Ra0.08;

[0065] S12: Clean the surface of base shaft 1 for 9-11 minutes, then clean it with ultrasound for 14-16 minutes, and finally blow it dry.

[0066] S11: Grind the surface roughness of the base shaft 1 to no greater than Ra0.08; this facilitates a tight bond between the copper film 3 formed by subsequent sputtering and the base shaft 1; if the surface roughness of the base shaft 1 is too large, the surface roughness of the prepared copper film 2 will also be too large; if the surface roughness of the base shaft 1 is too low, the surface area of ​​the copper film 2 bonded to the base shaft 1 will be smaller, resulting in poor bonding force.

[0067] S12: Clean the surface of base shaft 1 for 9-11 minutes, then clean it with ultrasound for 14-16 minutes, and finally blow it dry to remove surface impurities; this improves the cleanliness of the surface of base shaft 1 and facilitates subsequent work.

[0068] Preferably, step two includes,

[0069] S21: Place the copper target on top of the magnetron sputtering chamber and evacuate the chamber to a pressure not exceeding 5 × 10⁻⁶. - 5 Pa; Evacuate the magnetron sputtering chamber to reduce the amount of oxidizing gas and other gases that are detrimental to the sputtering of the copper film 2.

[0070] S22: Apply a voltage of -348V to -352V to the copper target while sputtering the copper target with argon gas at a flow rate of not less than 30 sccm, maintaining the pressure in the magnetron sputtering chamber at 0.4Pa to 0.5Pa. This process lasts for 2.5 to 3.5 minutes, removing impurities and oxide films from the copper target surface. Preferably, the copper content of the copper target is above 99.9%. sccm is cubic centimeters per minute.

[0071] S23: Stop applying voltage to the copper target, place base shaft 1 on top of the magnetron sputtering chamber, and evacuate the magnetron sputtering chamber to a pressure not exceeding 5 × 10⁻⁶. -5 At the same time, argon gas continues to sputter the copper target at a flow rate of not less than 30 sccm, while maintaining the pressure in the magnetron sputtering chamber at no more than 0.5 Pa and the temperature in the sputtering chamber between 50°C and 80°C. This process lasts for 45 to 55 minutes, forming a copper film with a thickness between 3 μm and 4 μm.

[0072] Preferably, S12 includes: cleaning the surface of the base shaft 1 with acetone, ultrasonically cleaning with anhydrous ethanol, and drying with nitrogen.

[0073] Preferably, the rigid film is an H-DLC film, and step three includes:

[0074] S31: Replace the copper target with a graphite target with a purity of not less than 99.9% and place it on top of the magnetron sputtering chamber. Evacuate the magnetron sputtering chamber to a pressure not exceeding 5 × 10⁻⁶. -5 Pa, with a temperature range of 480℃ to 520℃;

[0075] S32: Apply a substrate bias voltage of -348V to -352V to the graphite target, while sputtering the graphite target with a mixed gas of argon and methane at a flow rate of not less than 150 sccm, wherein the ratio of argon to methane is between 2.2 and 2.3. This process lasts for 20 to 25 hours to form an H-DLC film with a thickness between 3 μm and 4 μm.

[0076] Preferably, step three further includes,

[0077] S33: Cool the temperature inside the sputtering chamber to between 25°C and 30°C at a rate of (0.3-0.4)°C / min. Cool slowly to avoid excessively rapid cooling that could prevent the effective release of stress on the base shaft 1, copper film 2, and H-DLC itself.

[0078] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A rotating shaft, comprising a base shaft (1), wherein the base shaft (1) is made of an iron-based alloy, and the surface of the base shaft (1) is covered with a hard film (2), wherein the hardness of the hard film (2) is greater than the hardness of the base shaft (1), characterized in that, Only a copper film (3) is provided between the base shaft (1) and the hard film (2), and the hardness of the copper film (3) is less than that of the base shaft (1); The copper film (3) can improve the bonding force between the base shaft (1) and the hard film (2) and reduce the residual internal stress of the hard film (2); The hard film (2) is a hydrogenated diamond-like material.

2. A pivot according to claim 1, characterised in that The thickness of the copper film (3) is H1, then 0.003mm≤H1≤0.004mm.

3. A hinge according to any one of claims 1-2, characterized in that The thickness of the hard film (2) is H2, then 0.003mm≤H2≤0.004mm.

4. An air circulating machine characterized by, It includes an air dynamic bearing (4) and a rotating shaft as described in any one of claims 1-3, wherein the top foil of the air dynamic bearing (4) is opposite to the outer peripheral surface of the rotating shaft.

5. A method of manufacturing a rotating shaft, characterized by, The manufacturing method is used for manufacturing the rotating shaft according to any one of claims 1-3; The manufacturing method includes: Step 1, processing the surface of the base shaft (1); Step 2, manufacturing a copper film on the surface of the base shaft (1); Step 3, manufacturing a hard film on the surface of the copper film.

6. The method for manufacturing a rotating shaft according to claim 5, characterized in that, The base shaft (1) is an iron base shaft (1), and step one includes: S11: grinding the surface roughness of the base shaft (1) to no greater than Ra0.08; S12: Clean the surface of the base shaft (1) for 9-11 minutes, then clean it with ultrasonic for 14-16 minutes, and finally blow it dry.

7. The method for manufacturing a rotating shaft according to claim 5, characterized in that, Step two includes, S21: Place the copper target on top of the magnetron sputtering chamber and evacuate the chamber to a pressure not exceeding 5 × 10⁻⁶. -5 Pa; S22: Apply a voltage of -348V to -352V to the copper target while sputtering the copper target with argon gas at a flow rate of not less than 30 sccm, and maintain the pressure in the magnetron sputtering chamber at 0.4Pa to 0.5Pa. This process lasts for 2.5 to 3.5 minutes. S23: Stop applying voltage to the copper target, place the base shaft (1) on top of the magnetron sputtering chamber, and evacuate the magnetron sputtering chamber to a pressure not exceeding 5 × 10⁻⁶. -5 At the same time, argon gas continues to sputter the copper target at a flow rate of not less than 30 sccm, while maintaining the pressure in the magnetron sputtering chamber at no more than 0.5 Pa and the temperature in the sputtering chamber between 50°C and 80°C. This process lasts for 45 to 55 minutes.

8. The manufacturing method of a pivot shaft according to claim 6, wherein S12 includes: cleaning the surface of the base shaft (1) with acetone, ultrasonically cleaning with anhydrous ethanol, and drying with nitrogen.

9. The method for manufacturing a rotating shaft according to claim 6, characterized in that, The rigid film is an H-DLC film, and step three includes... S31: Replace the copper target with a graphite target with a purity of not less than 99.9% and place it on top of the magnetron sputtering chamber. Evacuate the magnetron sputtering chamber to a pressure not exceeding 5 × 10⁻⁶. -5 Pa, with a temperature range of 480℃ to 520℃; S32: Apply a base bias voltage of -348V to -352V to the graphite target, while sputtering a mixture of argon and methane at a flow rate of not less than 150 sccm, wherein the ratio of argon to methane is between 2.2 and 2.5, and the process lasts for 20 to 25 hours.

10. The method for manufacturing a rotating shaft according to claim 9, characterized in that, Step three also includes, S33: Cool the temperature inside the sputtering chamber to between 25°C and 30°C at a rate of (0.3~0.4)°C / min.

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